Labour's lead over the Conservatives has shrunk from seven to just five points in the last fortnight, suggesting that David Cameron has not suffered any real damage in the eyes of the public from his House of Commons defeat over Syria.

The latest Opinium/Observer poll puts Labour on 35% (down one percentage point compared with two weeks ago), the Conservatives on 30% (up one percentage point), Ukip on 17% (down one percentage point) and the Liberal Democrats on 7% (down one percentage point).

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Cameron's net approval rating also offers some good news for the Tories, standing at -15 (compared with -18 in the last poll). This represents the biggest lead over Ed Miliband since before the 2012 budget. Miliband is on -31, though his net score has not deteriorated since the last poll.

On the eve of the Trades Union Congress, which opens in Bournemouth on Sunday, likely voters were also asked about Labour's links with the unions, and what effect Ed Miliband's handling of the issue might have on their decisions at the next election.

Rather than being hugely exercised by the subject, most voters seemed indifferent. Asked if they would be more or less likely to vote Labour if the party became less reliant on union funding, 65% said it would make no difference, while 18% said it would make them less likely to vote Labour and 17% said it would make them more likely to do so.

Credit: Observer graphics Observer graphic

Perhaps more significantly, only 17% said Ed Miliband's leadership was a reason why they would vote Labour, while 55% said it was a reason not to do so. Over a quarter (27%) said Labour's handling of the economy was a reason in favour of voting Labour, while 48% said it was a reason not do so.

On Syria, opinion was more evenly balanced, with 29% of voters saying its handling of the Syria issue was a reason to favour Labour while 31% said it was a reason not to back the party.